Github
CVE-2026-2266
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding, context-aware escaping
MITRE ATT&CK
2 techniques across 2 tactics: Initial Access, Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS 5.4 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: Low. User interaction: Required. Exploitation requires authentication. |
| Exploit ScenarioDerived | An attacker (requires authentication) could exploit this vulnerability to compromise the affected system. |
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Alert meAnalysisAIv1 – Mar 12, 2026
DOM-based XSS in GitHub Enterprise Server prior to version 3.20 allows authenticated attackers to execute arbitrary JavaScript in other users' browsers by injecting malicious HTML through task list content in issues and pull requests. The vulnerability stems from improper input neutralization in the task list rendering logic, which fails to re-encode user-supplied content before display. An attacker with repository access could exploit this to steal session tokens or perform actions on behalf of other users.
Earlier versions of this analysis (1)
An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed DOM-based cross-site scripting via task list content. [CVSS 5.4 MEDIUM]
RemediationAI
Monitor vendor advisories for a patch. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Enterprise Server. An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed DOM-based cross-site scripting via task list content. The task list content extraction logic did not properly re-encode browser-decoded text nodes before rendering, allowing user-supplied HTML to be injected into the page. An authenticated attacker could craft malicious task list items in issues or pull requests to execute arbitrary scripts in the context of another user's browser session. T
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
DescriptionGitHub Advisory
An improper neutralization of input vulnerability was identified in GitHub Enterprise Server that allowed DOM-based cross-site scripting via task list content. The task list content extraction logic did not properly re-encode browser-decoded text nodes before rendering, allowing user-supplied HTML to be injected into the page. An authenticated attacker could craft malicious task list items in issues or pull requests to execute arbitrary scripts in the context of another user's browser session. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.20 and was fixed in versions 3.18.6 and 3.19.3. This vulnerability was reported via the GitHub Bug Bounty program.
Executive ViewAI
Organizations using An improper neutralization of input vulnerability should be aware of moderate risk from CVE-2026-2266, a cross-site scripting vulnerability rated CVSS 5.4. Attackers could inject scripts to steal sessions or perform actions as authenticated users. Organizations should apply vendor updates when available and monitor for exploitation.
Apply vendor patch. If patching is delayed: implement CSP headers, enable HttpOnly cookies, deploy WAF XSS rules.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.
Affected Products (CPE)GitHub Advisory
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